1. Field of the Invention
This invention relates to enzyme granules containing at least two different enzymes, to a process for their production and to the use of the granules in solid or liquid detergents and cleaning formulations.
2. Statement of Related Art
Enzymes, especially proteases, are widely used in detergents, washing aids and cleaning products. Normally, the enzymes are not used as pure substances, but rather in the form of mixtures with a diluent/carrier material. If enzyme preparations of this type are added to conventional detergents, a considerable reduction in enzyme activity can occur during storage, especially if bleaching-active compounds are present. Application of the enzymes to carrier salts and simultaneous granulation in accordance with DE-OS 16 17 190 or by bonding using nonionic surfactants in accordance with DE-OS 16 17 188 or aqueous solutions of cellulose ethers in accordance with DE-OS 17 67 568 does not lead to a significant improvement in storage stability because the sensitive enzymes are generally situated on the surface of the carrier in mixtures of the type in question. Although the stability of the enzymes in storage can be significantly increased by coating the enzymes with or encapsulating them in the carrier material and converting them into the required particle form by extrusion, pressing and spheronizing, as described for example in DE-PS 16 17 232, in DE-OS 20 32 768 and in DE-ASS 21 37 042 and 21 37 043, corresponding enzyme preparations have poor solubility properties. The undissolved particles can become caught up in and thus soil the washing or pass into the wastewater without being used. Although the encapsulating compositions known from DE-OS 18 03 099, which consist of a mixture of solid acids or acidic salts and carbonates or bicarbonates and which disintegrate on addition of water, improve the solubility of the enzyme preparations, they are extremely sensitive to moisture and, accordingly, require additional protective measures. Another disadvantage of the above-mentioned preparation is that the enzymes can only be processed in the form of dry powders. The fermenter broths typically accumulating in the enzyme production process cannot be used in this form, but have to be freed from water beforehand.
EP 168 526 describes enzyme granules which contain water-swellable starch, zeolite and a water-soluble granulation aid. This document proposes a production process for such formulations which overcomes the problem mentioned above and which essentially comprises concentrating a fermenter solution freed from insoluble constituents, introducing the additives mentioned and granulating the resulting mixture. The process using the additive mixture proposed therein is advantageously carried out with fermentation solutions which have been concentrated to a relatively high dry matter content, for example of 55% by weight.
International patent application WO 92/11347 describes enzyme granules for use in granular detergents and cleaning compositions which contain 2% by weight to 20% by weight of enzyme, 10% by weight to 50% by weight of swellable starch, 5% by weight to 50% by weight of water-soluble organic polymer as granulation aid, 10% by weight to 35% by weight of cereal flour and 3% by weight to 12% by weight of water. These additives enable the enzyme to be processed without significant losses of activity. In addition, the storage stability of the enzymes in the granules is also satisfactory.
As demonstrated by way of example by the documents cited above, a broad prior art exists in the field of the production of granular enzyme preparations, so that various possibilities for making up individual enzymes in particulate form are available to the expert. Unfortunately, the methods mentioned fail when two or more enzymes capable of reacting with one another are to be incorporated in the same granule. This problem arises in particular in connection with protease which, as a protein-degrading enzyme, is of course capable of decomposing a second enzyme and/or other enzyme present at the same time. If this decomposition process takes place during the production and/or storage of the enzyme granules, the effect of the second enzyme and/or other enzymes under in-use conditions is no longer guaranteed.
Solutions to this problem have also been proposed in the prior art. Thus, according to International patent application WO 90/09440, two-enzyme granules are produced by coating a protease- and cellulose-containing core with a total of 10 layers (alternately stearic acid/palmitic acid glyceride and kaolin) the quantity of protective coating material in the Examples exceeding the quantity of core, subsequently applying a mixture of a second enzyme, a binder, a filler and a granulation aid and, finally, applying an outer coating. A production process such as this is unfavorable on account of the large amount of separating material required between the enzyme-containing core and the layer containing the second enzyme which lies further to the outside. Another disadvantage can be that, under in-use conditions, the enzyme on the outside dissolves first, the second enzyme only being released from the core at a later stage so that the two enzymes are unable to develop their effects at the same time.
Hitherto unpublished German patent application DE 43 29 463 describes a process for the production of multi-enzyme granules in which two separately prepared batches of granules differing in size and each containing an enzyme are agglomerated in a subsequent co-granulation step.
It is known from European patent application EP 304 332 that enzyme-containing basic granules can be coated with powder-form components containing a second enzyme. However, this method of producing multi-enzyme granules often leads to inadequate stability of the second enzyme present in the outer layer which, in addition, has to be prepared beforehand in powder form--another disadvantage of this method. In this variant, too, the two enzymes are generally not released simultaneously in the wash or cleaning liquor.